kcat
Do I require extra files for HRTF to work?
Would I need to download https://github.com/kosumosu/x3daudio1_7_hrtf for HRTF to function?
That's unrelated to DSOAL. That's for games that use the XAudio API, while DSOAL is for games that use the DirectSound API and converts the DSound API calls to OpenAL API calls. For DSOAL, OpenAL Soft comes with HRTF support, and should use it automatically if the device is reported to apps as headphones. Though it seems systems don't often do that for whatever reason, and may need a custom alsoft.ini to enable it. Simply creating an alsoft.ini file in the same folder as the game's executable, and add the lines:
[general]
stereo-encoding=hrtf
That should enable HRTF for that game.
If that's not enough, Windows speaker might be set to a quad/surround format, so you might also need channels=stereo.
If that's not enough, Windows speaker might be set to a quad/surround format, so you might also need
channels=stereo.
What if my headphones support 7.1 surround sound? I have Logitech G933 Headphones.
If it's set to anything but stereo in the Windows playback device speaker configuration then yeah you'll probably need it. Though if it has its own Logitech HRTF so you'll wanna turn that off to use OpenAL Soft's HRTF
Can I use it with Dolby Atmos for headphones? Game outputs 5.1 sound, and Dolby/DTS/Sonic handles HRTF, for example
Atmos relies on the system's spatial sound, so unless it fails to detect surround output, it should work. Though you might wanna check out the documentation to set up 7.1.4 so that you also get height. That said, unless you use real Atmos with ceiling speakers/upfiring sound bar, it might be better to just use OpenAL Soft's HRTF because it has a lot more positional accuracy (hundreds if not thousands of "virtual speakers") compared to 12 in 7.1.4 which doesn't even include speakers below the listener AFAIK